1. Field of the Invention
This invention relates to a method for sealing a gas release valve adapted to be attached to a sealing container for packaging a commodity which will generate a small amount of gases during shelf storage, for example, roasted coffee beans, such that the valve covers a vent hole in the container whereby the valve allows the gas filling in the container given off from the commodity to escape from the container.
2. Prior Art
Conventional gas release valves typically include a base film having an aperture and a valve film superimposed on one surface of the base film to cover the aperture and to define a channel therebetween for releasing the gas to exterior through the aperture. Examples of the type of valve are known in the art as disclosed in Japanese Patent Application Kokai Nos. 32244/1981, 57069/1985, 6278/1988, and 6279/1988. It is also known to seal such a gas release valve by applying fluid sealant such as silicone fluid to the channel of the valve in order to smoothly open and close the channel as disclosed in Japanese Patent Publication No. 29501/1984, Japanese Patent Application Kokai No. 152551/1988, and Domke et al., U.S. Patent Re. 32,018 reissued Nov. 5, 1985. The sealing method of Japanese Patent Publication No. 29501/1984 applies sealant to an outer end portion of the channel, and the sealing method of Japanese Patent Application Kokai No. 152551/1988 applies sealant to a circumferential portion about the aperture in the channel.
The sealing method of Japanese Patent Publication No. 29501/1984 has several drawbacks. The method fails to evenly fill the channel with the sealant since the sealant does not readily spread throughout the channel, especially up to a remote portion of the channel. When the sealant is applied to the outer end portion of the channel, the sealant adheres near to the channel outer end, contaminating the periphery and surface of the valve and thus staining the packaging container to which the valve is attached.
An improvement over this sealing method is disclosed in Japanese Patent Application Kokai No. 152551/1988, which suffers from a similar drawback since a substantial portion of the sealant applied to the inner peripheral portion of the channel can remain there. When the valve is attached to the packaging container in registry with its vent hole, the sealant remaining near the circumference of the aperture in the channel will penetrate into the container through the vent hole, contaminating the contents.
Neither of the above-mentioned methods can ensure that the channel will be evenly filled with a desired amount of sealant. Since these methods achieve penetration of sealant throughout the channel largely by a capillary flow from one end to another end, it is difficult to control relative fractions of the sealant to spread over and to remain near the applied site.